Mystery surrounds the death of marathon runner Christopher Davies MBE whose car collided with a tree on the A1066 at Brettenham and passed away in hospital 17 days later.

Mr Davies had been driving his BMW 525 in the direction of Thetford around 11pm on January 11 when the car left the road and struck a tree. It would have been the 60th birthday of his late wife Rosemary, who died from cancer ten years earlier.

The 64-year-old, from Crickhowell in Wales but living at Falcon Avenue in Diss, had an exemplary military career and had completed 48 marathons.

He and his wife had been made MBEs in 2005 after fostering children of soldiers involved in the wars in Iraq and Afghanistan. Mr Davies himself served in Kosovo, Bosnia, Germany and Nepal.

Senior coroner Jacqueline Lake told the inquest into his death: “We just don’t know what happened.”

Farm worker Michael Towell was first on the scene, and said in a statement to Norfolk Coroner’s Court how he came across an “large amount of debris” in the road.

“If you knew the area you would drive with extreme caution,” he said. “On the day of the crash there was hardly anything else on the road.”

Mr Towell dialled 999 and “police arrived very quickly”. Mr Davies was airlifted to Addenbrooke’s Hospital in Cambridge with serious injuries. The hospital had been the chosen charity for his most recent marathons.

Dr Anna Street, of the neurosurgical team at Addenbrooke’s, said in a statement Mr Davies had been “completely unresponsive” at the scene.

“Over the next 10 days he had multiple problems,” she said. “His situation was held but he did not wake up properly.”

After an MRI scan on January 19, Dr Street said: “It was felt given the severity of the head injury and poor neurological function his prognosis was poor. It was decided active treatment would be withdrawn.”

The cause of death was given as a traumatic brain injury.

Collision investigator PC Forbes-Scott said a number of factors had been considered for the cause of the crash including an animal loose in the road or Mr Davies falling asleep, but concluded: “The exact reason why he left the carriageway remains unknown.”

Mrs Lake recorded a conclusion of road traffic collision, adding: “It has to go unanswered.”

Bedside vigil held for two weeks

After the hearing Mr Davies’ sister Janette Davies issued a warning to drivers.

“Whatever you are driving is more powerful than you think,” she said. “Whenever I see a BMW now I hope for them to be careful.”

She said she was not disappointed by the conclusion of the inquest.

“If he did try to avoid an animal then I felt toward Chris,” she said. “There is always that sensitive part of him that would not have wanted an animal to die.

“A road traffic collision is so sudden, and he was incredibly fit. The doctors said he was like a 50-year-old.”

She said it was impossible Mr Davies would have been drinking as he was a tee-total and a member of the Salvation Army.

She added the care from nurses and doctors at Addenbrooke’s was “brilliant”.